This invention pertains to coupling means for a motor and a nozzle in an electro-hydraulic control structure which enables accurate adjustment of the spacing between the motor and nozzle after the components are assembled. The structure is not subject to incorrect assembly, movement when in service due to wear or vibration and not easily tampered with by persons attempting repair in the field.
There are many pressure-responsive devices that respond to a pilot pressure and more particularly to a differential pilot pressure. Such differential pilot pressure can be applied directly to an operating system, such as the displacement control for a pump as shown in Hann et al U.S. Pat. No. 3,359,727. The differential pilot pressure can also be used as the first stage of a two-stage control, with the second stage being, as an example, a displacement control valve, such as shown in the Crull U.S. Pat. No. 3,946,560.
Electro-hydraulic control structures are known wherein the differential pilot pressure is obtained by controlling the flow through a pair of nozzles associated with a pair of pilot lines and with the control of flow through the nozzles being by means of a member positionable by an electric motor. Typical control structures of this type are shown in U.S. Pat. Nos. 2,625,136; 2,924,241; and 3,023,782. In such structures, a pressure differential between the two pilot lines is determined by positioning of the member relative to nozzles through which fluid flows. The location and spacing of the nozzles relative to such member when in a centered position is critical as this affects the pilot pressure obtained at any operative position of the member. As illustrated in the Bauer U.S. Pat. No. 2,924,241, there are a pair of opposed nozzles with a movable member operable by a motor associated therebetween and the nozzles are rotatably mounted within a housing for adjustment. Such adjustment is time-consuming and difficult to maintain over an extended period of use. Additionally, the proper setting of the structure can be easily tampered with by unknowledgeable field repair persons.
It is also known to mount the nozzles to the motor by means of a press fit, with such mounting being tamper-resistant, but being difficult to initially adjust because of the uncertain friction characteristics of press-fit relation between the parts with the added requirement for more precision in the manufacture of the parts.
A linear electrical motor of the type utilized in the invention disclosed herein is shown in Casey U.S. Pat. No. 3,740,594.